It is somewhat version-controlled but not completely. If you use the reflog you can find it again and you can find how it moved around. But the reflog gets rewritten and gc'd so it's not true vc.
Just curious, why do you want that to be version controlled?
Because I might realize later I made a mistake, or I might want to view history.
I’d I never cared about historical state and mistakes, I wouldn’t need version control at all :)
You could delete the branches locally while archiving them to any another clone of the repo.